The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Cooling fan assemblies may provide airflow to dissipate heat generated by electronic components. Cooling fan assemblies may include a motor that drives fan blades via a rotor. The rotor may be restricted from rotating (hereinafter “restricted”) when an object is placed in the path of the fan blades. Airflow is reduced when the rotor is restricted. Accordingly, the electronic components may be thermally damaged due to a decrease in heat dissipation when the rotor is restricted.
Referring now to FIG. 1, a cooling fan system 100 includes a motor 102 and a motor control module 104. The motor 102 may include a two-phase brushless direct current (DC) motor. The motor 102 may include four stator poles: pole A1 106, pole A2 108, pole B1 110, and pole B2 112. Each of the stator poles may be wound with stator coils 114. Pole A1 106 and pole A2 108 may collectively be called “pole pair A.” Pole B1 110 and pole B2 112 may collectively be called “pole pair B.” The motor control module 104 may apply a voltage and/or current to the stator coils 114 of pole pair A to generate a magnetic field between pole A1 106 and pole A2 108. Applying the voltage and/or current to the stator coils 114 of pole pair A may be called “driving phase A.” The motor control module 104 may provide the voltage and/or current to the stator coils 114 of pole pair B to generate a magnetic field between pole B1 110 and pole B2 112. Applying the voltage and/or current to the stator coils 114 of pole pair B may be called “driving phase B.”
The motor 102 includes a rotor 116. The rotor 116 may include at least one permanent magnet. The motor control module 104 may drive phase A and/or phase B to actuate the rotor 116 about an axle 118. The axle 118 may mechanically couple the rotor 116 to a device. For example, the axle 118 may mechanically couple the rotor 116 to a fan 120 used to cool electronic components. While the rotor 116 in FIG. 1 rotates between the stator poles 106, 108, 110, 112, the motor 102 may include a rotor that surrounds the stator poles 106, 108, 110, 112.
The motor control module 104 may alternate between driving phase A and driving phase B to actuate the rotor 116. The motor 102 may include at least one Hall-effect sensor 122 that indicates rotation of the rotor 116. For example, the Hall-effect sensor 122 may generate a pulse when a magnetic pole of the rotor 116 passes the Hall-effect sensor 122. The motor control module 104 may determine whether the rotor 116 is rotating based on the pulses from the Hall-effect sensor 122. Accordingly, the motor control module 104 may determine that the rotor 116 is restricted based on the pulses. For example, the motor control module 104 may determine that the rotor 116 is restricted when the motor control module 104 receives no pulses from the Hall-effect sensor 122. When the motor 102 drives the fan 120, the rotor 116 may be restricted when an object is placed in the path of the fan 120.